Exemplary embodiments of the present invention relate to a semiconductor device and a method for fabricating the same, and more particularly, to a semiconductor device with a buried gate and a method for fabricating the same.
Recently, a fabrication process of a semiconductor device, such as a dynamic random access memory (DRAM), has been developed to improve integration degree. As the semiconductor device is highly integrated, two important concerns regarding the fabrication process arise. The first concern regards the degradation of contact holes when the fine patterns are formed. The second concern regards the guarantee of capacitance of capacitors.
In order to address the above concerns, the reliability of the semiconductor device may be secured by applying a buried gate to the semiconductor device.
FIG. 1 is a cross-sectional view illustrating a conventional semiconductor device with a buried gate.
Referring to FIG. 1, the conventional semiconductor device with the buried gate includes a semiconductor substrate 11, a device isolation layer 12 formed by etching a portion of the semiconductor substrate 11, an active region 13 defined by the device isolation layer 12 in the semiconductor substrate 11, a trench 14 formed by etching portions of the active region 13 and the device isolation layer 12, a gate insulation layer 15 formed over the surface of the trench 14 in the active region 13, a buried gate 16 filling a portion of the trench 14, and an interlayer insulation layer 17 formed over the buried gate 16 and filling the remainder of the trench 14.
The buried gate 16 is formed of a metal layer, and the device isolation layer 12 is formed of an oxide layer.
In the conventional semiconductor device with the buried gate, because the buried gate 16 makes direct contact with the device isolation layer 12, deterioration (e.g., the oxidation 18) of the buried gate 16 occurs when a reaction takes place between the buried gate 16 and the device isolation layer 12. Further, the reliability of the semiconductor device is degraded due to the deterioration of the buried gate 16.
Also, the buried gate of the conventional semiconductor device is easily oxidized by a subsequent thermal process such as an interlayer insulation formation process.